Hide topbar when mobile orientation in landscape mode (resolve #459)

_javascript/commons/topbar-switcher.js

@@ -0,0 +1,90 @@
+/*
+ * Hide Header on scroll down
+ */
+
+$(function() {
+  const $searchInput = $("#search-input");
+  const delta = ScrollHelper.getTopbarHeight();
+
+  let didScroll;
+  let lastScrollTop = 0;
+
+  function hasScrolled() {
+    let st = $(this).scrollTop();
+
+    /* Make sure they scroll more than delta */
+    if (Math.abs(lastScrollTop - st) <= delta) {
+      return;
+    }
+
+    if (st > lastScrollTop ) { // Scroll Down
+      ScrollHelper.hideTopbar();
+
+      if ($searchInput.is(":focus")) {
+        $searchInput.blur(); /* remove focus */
+      }
+
+    } else  { // Scroll up
+      // has not yet scrolled to the bottom of the screen, that is, there is still space for scrolling
+      if (st + $(window).height() < $(document).height()) {
+
+        if (ScrollHelper.hasScrollUpTask()) {
+          return;
+        }
+
+        if (ScrollHelper.topbarLocked()) { // avoid redundant scroll up event from smooth scrolling
+          ScrollHelper.unlockTopbar();
+        } else {
+          if (ScrollHelper.orientationLocked()) { // avoid device auto scroll up on orientation change
+            ScrollHelper.unLockOrientation();
+          } else {
+            ScrollHelper.showTopbar();
+          }
+        }
+      }
+    }
+
+    lastScrollTop = st;
+
+  } // hasScrolled()
+
+  function handleLandscape() {
+    if ($(window).scrollTop() === 0) {
+      return;
+    }
+    ScrollHelper.lockOrientation();
+    ScrollHelper.hideTopbar();
+  }
+
+  if (screen.orientation) {
+    screen.orientation.onchange = () => {
+      const type = screen.orientation.type;
+      if (type ===  "landscape-primary" || type === "landscape-secondary") {
+        handleLandscape();
+      }
+    };
+
+  } else {
+    // for the browsers that not support `window.screen.orientation` API
+    $(window).on("orientationchange",() => {
+      if ($(window).width() < $(window).height()) { // before rotating, it is still in portrait mode.
+        handleLandscape();
+      }
+    });
+  }
+
+  $(window).scroll(() => {
+    if (didScroll) {
+      return;
+    }
+    didScroll = true;
+  });
+
+  setInterval(() => {
+    if (didScroll) {
+      hasScrolled();
+      didScroll = false;
+    }
+  }, 250);
+
+});